Lion Air jet should have been grounded before fatal crash

The flight from Bali to Jakarta on 28 October had experienced similar technical issues to the doomed flight the next day from Jakarta to Pangkal Pinang, said Nurcahyo Utomo, head of Indonesia's national transport safety committee (KNKT).

Pilots experienced several problems with the aircraft in the days leading up to the October 29 crash, investigators said - including a faulty airspeed sensor, altitude indicators and angle-of-attack sensors that should have grounded the plane.

Although the initial report doesn't assign definitive cause to the accident, the NTSC was blunt about the airline's maintenance: "In our opinion, the plane was no longer airworthy and it should not have continued", Nurcahyo Utomo, the NTSC's aviation lead, told reporters at a press briefing on Wednesday in Indonesia.

It said that the preliminary report showed that the correct procedures to counter the plane's nose being pushed down were carried out during the Denpasar flight the day before the crash.

In the disaster's immediate aftermath, pilots for several airlines placed blame on Boeing for reportedly failing to provide information about the anti-stalling feature in its Max 8 and 9 aircraft.

"It's all consistent with the hypothesis of this problem with the M.C.A.S. system", said R. John Hansman Jr., a professor of aeronautics and astronautics and director of the worldwide centre for air transportation at the Massachusetts Institute of Technology.

The pilots of that flight reported problems to Lion Air's maintenance team, which checked the jet and cleared it for take-off the next morning.

If the automatic system kicked in and "the pilot didn't know what was happening", there was a risk it would confuse the pilots, he added.

But if the sensors were not sending the correct data to the MCAS system, the software likely calculated that the aircraft was approaching stall conditions while it was well within normal flight conditions during takeoff, pushing the aircraft into a dive. Its new automated system pushes the nose down if a sensor detects that the nose is pointed so high the plane could go into an aerodynamic stall.

The Indonesian National Transportation Safety Committee has retrieved one of the plane's black boxes - the flight data recorder - but is yet to locate the cockpit voice recorder.

As for the potentially malfunctioning sensor, the doomed plane had experienced incorrect data readings on its three previous flights-even after the sensor was replaced, CBS News reports.

"There were four flights that experienced problems with the airspeed indicator", Tjahjono said. They were able to complete the flight and land the plane safely. Before crashing, the pilot asked to return to the airport, but couldn't.

Boeing said it is cooperating with investigators. But a Boeing spokesperson said that "the appropriate flight crew response to uncommanded trim, regardless of cause, is contained in existing procedures" within the flight manual for the 737 MAX, and company officials felt that additional details of the new system weren't necessary.

Members of the National Transportation Safety Committee lift a box containing the flight data recorder from a crashed Lion Air jet.

The 737 Max is the most popular plane in Boeing history, with 453 delivered so far and 4,671 on order.

The airline, which also operates Batik Air and Wings Air, has a dubious safety record, though, and has had more accidents than other airlines in the country.

The investigation is continuing with help from USA regulators and Boeing.

  • Rogelio Becker